This invention is concerned with a method for the storage of blood platelets in a plasma-free medium. Also described is a platelet concentrate obtained by this method.
Thrombocytopenia means low platelet counts in the circulatory system. Persons with this disease have a tendency to bleed as do hemophiliacs, except that the bleeding is usually from many small capillaries rather than from large vessels as in hemophilia. Such persons suffer small punctate hemorrhages throughout all the body tissues. The skin of such a person will exhibit many small, purplish blotches. Platelets are especially important for repair of minute breaks in capillaries and other small vessels. Platelets aglutinate to fill such ruptures without actually causing clots.
Normally, excessive bleeding does not occur until the number of platelets in the blood falls below a value of approximately 70,000 per cubic millimeter rather than the normal of 150,000 to 350,000.
At the present time, persons who have low platelet counts are supported by infusion of platelet concentrates. Platelet concentrates contain on average 6.times.10.sup.10 platelets suspended in a volume of 50-60 ml of plasma. Larger platelet concentrates can be obtained using apheresis machinery, in which case the concentration is in the range of 4.times.10.sup.11 and the plasma volume may reach 200-300 ml. Platelet concentrates can be kept for 3, 5 or even 7 days, depending on the type of bag and mode of rotation used.
There are generally speaking two types of blood collection and storage bags available. One type permits storage of platelets in plasma for up to 3 days while another type permits storage of platelets in plasma for up to 5 days and sometimes up to 7 days. The latter type is generally used for research purposes. In addition it should be noted that platelet storage bags must not contain the plasticizer di-2-ethyl-hexylphthalate and they should be highly permeable. While stored, all bags are subjected to rotation on a continuous basis which can be rotational about a transverse axis or horizontal and reciprocal or horizontal and circular.